A color filter method and a field-sequential method are known as display methods of liquid crystal display devices. In a liquid crystal display device in which images are displayed by a color filter method, a plurality of subpixels each having a color filter that transmits only light with a wavelength of one color (e.g., red (R), green (G), or blue (B)) are provided in each pixel. A desired color is produced in such a manner that transmittance of white light is controlled per subpixel and a plurality of colors is mixed per pixel. On the other hand, in a liquid crystal display device in which images are displayed by a field-sequential method, a plurality of light sources that emit lights of different colors (e.g., red (R), green (G), and blue (B)) are provided. A desired color is produced in such a manner that the plurality of light sources sequentially turned on and transmittance of light of each color is controlled per pixel. In other words, a desired color is realized with division of the area of one pixel into respective areas for respective lights of colors according to the color filter method; a desired color is realized with division of the display period into respective display periods for respective lights of colors according to the field-sequential method.
The liquid crystal display device employing a field-sequential method has the following advantages over the liquid crystal display device employing a color filter method. First, in the liquid crystal display device employing a field-sequential method, it is not necessary to provide subpixels in each pixel. Thus, the aperture ratio can be improved or the number of pixels can be increased. In addition, in the liquid crystal display device employing a field-sequential method, it is not necessary to provide a color filter. That is, loss of light due to light absorption in the color filter does not occur. Therefore, light transmittance can be improved and power consumption can be reduced.
Patent Document 1 discloses a liquid crystal display device in which images are displayed by a field-sequential method. Specifically, Patent Document 1 discloses a liquid crystal display device in which each pixel includes a transistor for controlling input of an image signal, a signal storage capacitor for retaining the image signal, and a transistor for controlling charge transfer from the signal storage capacitor to a display pixel capacitor. In the liquid crystal display device having this configuration, image signal writing to the signal storage capacitor and display in accordance with electric charge retained in the display pixel capacitor can be performed in parallel.